 /*******************************************************************************
  * Copyright (c) 2000, 2006 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  *******************************************************************************/

 package org.eclipse.ui.activities;

 import java.util.Set ;

 /**
  * An instance of this interface can be obtained from an instance of
  * <code>IActivityManager</code>for any identifier.
  * <p>
  * An <code>IIdentifier</code> is an object that offers an easy means to
  * determine if a given string matches the pattern bindings of any IActivity
  * objects. Additionaly, one may query if an identifier is enabled. An
  * identifier is always considered enabled unless it matches only disabled activities.
  * </p>
  * <p>
  * The handle-based nature of this API allows it to work well with runtime
  * plugin activation and deactivation, which can cause dynamic changes to the
  * extension registry.
  * </p>
  * <p>
  * This interface is not intended to be extended or implemented by clients.
  * </p>
  *
  * @since 3.0
  * @see IActivityManager#getIdentifier(String)
  */
 public interface IIdentifier extends Comparable {

     /**
      * Registers an instance of <code>IIdentifierListener</code> to listen
      * for changes to properties of this instance.
      *
      * @param identifierListener
      * the instance to register. Must not be <code>null</code>.
      * If an attempt is made to register an instance which is
      * already registered with this instance, no operation is
      * performed.
      */
     void addIdentifierListener(IIdentifierListener identifierListener);

     /**
      * Returns the set of activity ids that this instance matches. Each
      * activity in this set will have at least one pattern binding that matches
      * the string returned by {@link #getId()}.
      * <p>
      * Notification is sent to all registered listeners if this property
      * changes.
      * </p>
      *
      * @return the set of activity ids that this instance matches. This set may
      * be empty, but is guaranteed not to be <code>null</code>. If
      * this set is not empty, it is guaranteed to only contain
      * instances of <code>String</code>.
      */
     Set getActivityIds();

     /**
      * Returns the identifier of this instance.
      *
      * @return the identifier of this instance. Guaranteed not to be <code>null</code>.
      */
     String getId();

     /**
      * Returns whether or not this instance is enabled. An identifier is always
      * considered enabled unless it matches only disabled activities.
      *
      * <p>
      * Notification is sent to all registered listeners if this property
      * changes.
      * </p>
      *
      * @return <code>true</code>, iff this instance is enabled.
      */
     boolean isEnabled();

     /**
      * Removes an instance of <code>IIdentifierListener</code> listening
      * for changes to properties of this instance.
      *
      * @param identifierListener
      * the instance to remove. Must not be <code>null</code>.
      * If an attempt is made to remove an instance which is not
      * already registered with this instance, no operation is
      * performed.
      */
     void removeIdentifierListener(IIdentifierListener identifierListener);
 }

